Copper balls (ρ = 8933 kg/m3, k = 401 W/m·K, cp = 385 J/kg·°C, α = 1.166 × 10–4 m2/s) initially at 180°C are allowed to cool in air at 30°C for a period of 2 minutes. If the balls have a diameter of 2 cm and the heat transfer coefficient is 80 W/m2·K, the center temperature of the balls at the end of cooling is